Not long ago the idea of repairing the brain’s wiring to fight addiction would have seemed far-fetched. But advances in neuroscience have upended conventional notions about addiction—what it is, what can trigger it, and why quitting is so tough.

“Those who were born in the U.S.S.R. and those born after its collapse do not share a common experience,” wrote Svetlana Alexievich, who won the Nobel Prize in literature in 2015. “It’s like they’re from different planets.”